What morphology do nanocatalyst particles take on after heating?

Xiner Lu, Sooyeon Hwang, and Kai He at the University of California – Irvine and Brookhaven National Laboratory used the Hummingbird Scientific tomography TEM sample holder to perform to perform electron tomography of Pt-Ni nanoparticles after heating. Tomographic reconstructions of synthesized nanoparticles were combined with high-angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) and X-ray diffraction (XRD) to investigate structural and chemical evolution at elevated temperatures.

a) Atomic model showing the thermally induced structural evolution of a Pt-Ni nanoparticle through two stages including the facet development and the flattening effect. b) 3D visualization of a nanoparticle rendered from STEM tomography reconstruction. Surface rendering of the 3D reconstruction along (c) the projection view and (d) the side view. e) HAADF-STEM tomography tilt series images of a nanoparticle after heating. Copyright © 2024 American Chemical Society

Upon heating, facets develop from a truncated octahedron into a more spherical isotropic shape, followed by slight flattening into an ellipsoid due to surface atom migration as temperature approaches 800 °C. The ultra-stable tomography TEM holder enabled nanoscale 3D reconstruction of these ellipsoid geometries. The study provides new insights into bimetallic nanocatalyst evolution at high-temperature which will inform geometric and compositional optimization and accelerate development of high-performance and stable heterogeneous catalysts.

Reference: Xiner Lu, Sooyeon Hwang, Kai He ACS Applied Nano Materials 7  (13) 15735–15742 (2024) DOI: 10.1021/acsanm.4c02753

Full paper Copyright © 2024 American Chemical Society

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